"You can overbreath. When people at a gym or... jogging... [through heavy panting] you're offloading... too much CO2. You're causing constriction in your circulation. ...If you were to breath 30 deep breaths, you'll feel some tingling in your head... maybe your fingertips... your toes will get cool. That's not from an increase in oxygen, it's the opposite... a decrease in circulation."